(CNN) -- The phone-hacking scandal engulfing Rupert Murdoch's media empire intensified in the United States Wednesday as a veteran senator urged the Justice Department to investigate whether one of Murdoch's U.S.-based companies violated federal anti-bribery laws.

Sen. Frank Lautenberg, D-New Jersey, sent a letter to Attorney General Eric Holder asking Holder to look into concerns that News Corp. -- the parent company of Fox News -- violated the Foreign Corrupt Practices Act, known as the FCPA. The law, enacted in 1977, makes it illegal for a U.S. person or company to pay foreign officials to obtain or retain business.

News of the World, a 168-year-old British newspaper owned by Murdoch, printed its last edition Sunday in the wake of accusations that its reporters illegally eavesdropped on the phone messages of murder and terrorist victims, politicians and celebrities. Police in the United Kingdom have identified almost 4,000 potential targets of phone hacking.

There also were claims that reporters may have bribed law enforcement officers.

"The limited information already reported in this case raises serious questions about the legality of the conduct of News Corporation and its subsidiaries under the FCPA," Lautenberg wrote.

"Further investigation may reveal that current reports only scratch the surface of the problem at News Corporation. Accordingly, I am requesting that (the Justice Department) and the (Securities and Exchange Commission) examine these circumstances and determine whether U.S. laws have been violated."

Potential liability flows from journalists at News of the World to its parent, News International; to its parent, News Corp., which is a publicly held company in the United States.

Sen. Jay Rockefeller, D-West Virginia, said Tuesday he is concerned about whether journalists tapped into the phones of the victims of the September 11, 2001, terrorist attacks.

"The reported hacking by News Corporation newspapers against a range of individuals -- including children -- is offensive and a serious breach of journalistic ethics," Rockefeller said in a written statement. "This raises serious questions about whether the company has broken U.S. law, and I encourage the appropriate agencies to investigate to ensure that Americans have not had their privacy violated."

After the closure of News of the World, News International still owns The Sun, The Times and The Sunday Times in Britain. News Corp. encompasses not only Fox News, but also The Wall Street Journal, the New York Post and Harper Collins publishers.

"There does seem to be a basis for a U.S. investigation at this point," said Mike Koehler, a professor of business law at Butler University in Indianapolis.

But attorney Richard Cassin, who helps clients comply with the FCPA, said he believes a prosecution is unlikely.

"The chances are very slim unless the payments we know about turn out to be the tip of the iceberg," he said.

Cassin argued that U.S. authorities are likely to trust the British legal system -- older than America itself -- to handle the case. U.S. authorities usually go after cases that are not being prosecuted elsewhere and in which widespread, systematic bribery can be proved, Cassin said.

News Corp., he noted, does not fit the bill.

The biggest case for a FCPA violation to date involved the German company Siemens AG, which paid $1.36 billion in bribes to foreign officials working on projects including the United Nations' oil-for-food program in Iraq and others in Nigeria, Bangladesh, China, Russia and Vietnam.

The company paid a record $800 million in fines and penalties for the FCPA violation.

But the United States took on that case partly because Germany did not prosecute Siemens, Cassin said, for what amounted to widespread bribery.

However, were a U.S. case against News Corp. to arise, the potential implications for the Murdoch media empire are numerous -- and none of them are good, Koehler said.

An investigation would most certainly attempt to answer the question of how widespread bribes were within News Corp. Were other employees -- all over the world, for that matter -- making similar payments?

The FCPA stipulates that U.S.-listed companies, their employees or agents may not make bribes to foreign officials. A second portion of the law applies to accounting requirements for public companies, said Don Zarin, author of "Doing Business Under The Foreign Corrupt Practices Act" and a partner with the Washington-based law firm of Holland & Knight.

"They have to keep books and records in reasonable detail that reflect the transactions," he said.

So, if a bribe was made and not properly noted, the U.S. Securities and Exchange Commission and the Justice Department could each have a case, Zarin said.

A telephone call or an e-mail from an editor in London to his or her boss in New York could prove key, he said.

"If you send an e-mail to the boss saying, 'I'm going to pay $10,000 to police officers for this information,' that would provide the jurisdictional basis or potential liability on the part of possibly the British employees," Zarin said.

If any employee of News Corp., which is listed in the United States, knew about and authorized such a payment, "they could have potential exposure," he said.

And if Murdoch -- the 80-year-old Australian-born head of News Corp. who became a U.S. citizen in 1985 -- knew what was going on and authorized it, even implicitly, "he could have some potential exposure," Zarin said.

The penalties can be severe, including jail time and fines, he said. And ignorance confers no protection.

"The SEC has brought cases against U.S. companies who had no knowledge of what foreign subsidiaries were doing, but had misbooked it," he said, adding that the SEC blamed the companies for not having set up the internal controls that would have caught the illegal behavior.

A Justice spokeswoman said she could not comment on the possibility of the department's involvement.

If the charges wind up being nothing more than civil accounting violations, the SEC would handle the case and Justice would not become involved, said James Tillen, coordinator of the FCPA Practice Group at Miller and Chevalier, a Washington-based law firm specializing in international regulatory issues, tax and litigation.

That would still carry a major risk to those involved.

"The SEC has a lot of bite in significant fines, penalties, prohibiting people from serving as officers in public companies," he said. "That can derail a career quickly."

But a criminal prosecution by federal prosecutors would be the most to fear, since it would carry the potential of jail time, Tillen said.

SEC fines can range up to $25 million per violation in such cases, but totals regularly exceed $100 million because the agency can force the company to disgorge ill-gotten gains.

The Justice Department can impose a criminal fine on individuals of up to $100,000 and five years in prison for each count on a bribery charge, he said. Multiple counts could lead to higher fines and sequential prison terms.

But fines are typically pegged to how much a company or an individual gained as a result of the crime, Tillen said. That can be easy to figure out when the subject is a contract, but any case involving Murdoch's empire might present more of a challenge. "How many more newspapers did you sell?" he asked.

Still, U.S. authorities may choose not to intervene at all.

"If the Department of Justice were satisfied that the U.K. had sufficient ability to prosecute this, then they may step aside," Tillen said. "If they weren't satisfied, then they could be very interested."

England passed an aggressive law, the U.K. Bribery Act, which took effect July 1, but it is not retroactive, Tillen said. The predecessor legislation that would apply "is a hodgepodge" of laws, some of which date back more than a century, he said. "That's part of the problem."

As things now stand, the nearly 4,000 miles that separate Washington from London won't put off U.S. investigators. "Of the 10 largest fines in FCPA history, eight have been against foreign companies," Tillen said.

But that may change. Rep. James Sensenbrenner, R-Wisconsin, has criticized the act as putting U.S. companies at a competitive disadvantage and held hearings last month intended to water it down, Tillen said. "The criticism is that it's being overly enforced by SEC and DOJ to reach activities that it shouldn't reach," such as taking officials out for free meals, he said.

A spokeswoman for Sensenbrenner provided CNN with a statement Monday from the congressman.

"I plan to introduce a bill that would reform the Foreign Corrupt Practices Act and bring it up-to-date with the changing world," Sensenbrenner said in the statement. "We need to bring clarity to what is and what is not illegal. My intent is to make sure that the stop signs and red lights are clearly visible for American companies doing commerce internationally.

"Right now, there is confusion regarding who qualifies as a foreign official. Foreign law enforcement officers are clearly foreign officials and it is absolutely absurd to imply that any changes to the FCPA would change that status or permit U.S. businesses to bribe policemen," he added.